A silicon halide such as dichlorosilane is conventionally used as a starting material for silicon semiconductor. Recent years, the possibility of disilicon hexachloride has been considered to be expected as a CVD material for depositing silicon nitride layer at a low temperature compared with this dichlorosilane.
However, disilicon hexachloride, by whichever method it may be produced, contains a silanol as an impurity. So a high purity disilicon hexachloride is required for forming silicon nitride layer stably and a purification method for removing an impurity such as a silanol is demanded. If the impurity content is high, a deposition rate of silicon nitride may slow down. In addition, the impurity may be taken in the layer to lead a problem where a homogeneous layer may not be formed.
The purification method of a silicon chloride compound is disclosed, for example in JP-A H02-153815. This literature discloses an example where a chloro polysilane material is subjected to a contacting with activated carbon and then a distilling to purify.